1. Technical Field
The present disclosure relates to an apparatus and method for controlling a supply voltage using hierarchical performance monitors and, more particularly, to the apparatus and method for controlling the supply voltage using hierarchical performance monitors that monitor continuously whether a level of the supply voltage supplied to a system is suitable for a target operating frequency by using the hierarchical performance monitors, and capable of controlling the level of the supply voltage based on a monitoring result.
2. Discussion of the Related Art
A hardware performance monitor (hereinafter referred to as ‘HPM’) is modeled on a relationship between a supply voltage supplied to a circuit or a system and an operating speed of the circuit or the system, i.e. a target operating frequency, which is changed by the supply voltage. It is one of the key factors that may be applied to a variable supply voltage scheme such as a dynamic voltage scaling or a dynamically adjustable supply voltage, etc.
In a system using the variable supply voltage scheme, the HPM monitors continuously whether the level of the supply voltage supplied to the system is suitable for the target operating frequency that is supplied, or will be supplied, to the system, and controlling the level of the supply voltage according to the monitoring result.
Success or failure of the variable supply voltage scheme depends on finding the level of the supply voltage suitable for the target generating frequency of the system based on an exact monitoring result of the HPM, and which supply voltage level may minimize the energy consumption or the power consumption of the system.
However, in a design of a semiconductor chip, the inside of each domain of a chip may have slightly different characteristics of a supply voltage-target operating speed according to the tendency of an increase of the chip's size and complexity, a variety of the chip functions, and a CMOS technology scaling.
Also, the inside of each domain of the chip has a slightly different characteristic of the supply voltage-target operating speed due to an inequality in the manufacturing process. Each of the domains operates in as many different temperatures as there are differences in activity and/or a leakage current between each domain of the semiconductor chip or the systems that occur when the system including the semiconductor chip operates. Therefore, each domain of the system, including the inner part of the semiconductor chip, or each semiconductor chip has slightly different features of the supply voltage-target generating speed.